In our British Patent Specification Nos.: 1601917 and 1601918 we disclose a form of ammunition which comprises a hollow outer casing, a pressure cylinder within the casing, valve means at one end of the cylinder, and a missile located in a mouth at a nose end of the casing, the pressure cylinder being slidable within the casing to cause the valve means to open and permit compressed air, contained in the cylinder, to flow from the cylinder to the mouth of the casing to expel the missile. The ammunition can be recharged with compressed air and a new missile, so as to be readily re-useable. This ammunition is hereinafter referred to as "ammunition of sliding cylinder form".
The ammunition was desinged for use in a firearm, with temporary modification of the latter to provide a barrel sleeve and a blunt firing pin, or for use in a similar weapon permanently adapted only to accept such ammunition to enable missiles of air gun pellet form to be employed for qualification as an air gun and not as a firearm under the Laws of certain countries.
While such ammunition of sliding cylinder form was effective when initially tested in particular guns under laboratory conditions, further trials revealed many disadvantages some of which could not be overcome by prolonged development of, and engineering modifications to, the ammunition and the guns. (As a result, our alternative form of practise ammunition, described in our British Patent Specification No. 2044896A, was developed for production and is now in use). Said disadvantages included wide variations in the accuracy and velocity of missiles fired under identical conditions using apparently identical ammunition, difficulties in recharging and reloading the ammunition, premature discharge risks, and incompatibility of the gun/ammunition combination with the Laws of certain countries. Further, said developments and engineering modifications, while overcoming or reducing some disadvantages would have been excessively expensive if put into production.
More recently the inventor has made certain further discoveries and improvements concerning ammunition generally of sliding cylinder form, which improved ammunition is being developed in conjunction with a new form of gun to avoid the said disadvantages, and to provide an improved and effective weapons system e.g. for target shooting. However, these cartridges being developed by us are bulky and the gun is of a new form.
This new weapons system will, to a considerable extent, satisfy the need, mentioned in particular in said Specification No. 1601918, for means enabling persons to practice shooting, which offers a combination of the advantages of standard air guns with the advantages arising from using cartridge ammunition, without the costs and hazards involved in the use of explosive propellants. However, the new weapons system has certain inherent limitations. For example, the improved ammunition cartridges are only compatible with the type of gun being developed or a gun especially and extensively modified, they are relatively bulky, and the firing of the sliding cylinder ammunition gives rise to recoil characteristics which, although small, are different from those of firearms and known air guns.
The general problems of bulk and recoil are to some extent interrelated, e.g. to store a given amount of energy in the pressure cylinder, the bulk (volume) of the cylinder can be reduced if the pressure is increased, but increasing the pressure increases the force needed to open the discharge valve means and thus requires the firing pin of the gun to have a greater momentum which produces recoil when the firing pin strikes the pressure cylinder. These problems are inherently applicable to the ammunition of sliding cylinder form.
In our British Patent Specification No. 1601918 it is mentioned that between the years 1880 and 1900 there were various proposed forms of compressed air powered ammunition for use in a suitable weapon for shooting, without some of the cost and other disadvantages inherent in using firearms; but such proposals were unsuccessful for various reasons, and since then the idea seems to have been abandoned. In fact, in Swiss Pat. No. 16072 granted in 1898 to Dr. J. Meuli-Hilty there was proposed a cartridge of a different type, which comprises a cylindrical pressure casing, a movable member (in the form of a hollow tube co-axial with the casing) and two spaced apart fixed members in the form of stuffing boxes secured in the casing. The tube extended through the stuffing boxes and was provided with two openings spaced apart so as to be closed by the stuffing boxes when the tube was in a first predetermined position. The tube had one end portion closed by a valve, which end portion was exposed at a rear end of the cartridge, and had an opposite end portion which terminated within a front part of the casing to the rear of a bullet seated in a front end of the casing. A spring urged the tube rearwards to bring a stop on the opposite end portion of the tube into contact with a front one of the two stuffing boxes. The large space between the stuffing boxes could be charged with compressed gas by removing a nut from a rear end of the tube, opening the valve, and rotating the tube to bring a rear one of the ports into alignment with a passage in the rear stuffing box. Thereafter, the valve was closed, the nut was replaced, and the cartridge was discharged by driving the tube forwards towards the bullet thereby bringing the front port to a small space between the bullet and the front stuffing box thereby allowing gas to escape from the large space to the small space via a restricted path comprising the passage, the rear port, the interior of the tube and the front port.
This proposed form of cartridge having a pressure casing does not appear to have been successful, and the proposal does not appear to have given rise to any subsequent developments, possibly because of the disadvantages inherent in the cartridge, in particular:
(a) the discharge path provides a severe restriction upon the rate of gas discharge whereas a rapid discharge is necessary;
(b) the stuffing boxes used to cover the ports would not have been effective to retain gas at the high pressure required for long periods, and any attempt to provide effective seals would have given rise to considerable frictional resistance to movement of the tube, unless the latter had a very small diameter; and
(c) the procedure for charging the cartridge was complicated and required an externally accessible manually operable stop-cock form of valve.
However, this proposed form of cartridge having a pressure casing shows an item which is of interest. If the problem of sealing is ignored, for any given construction of the cartridge the force needed to move the tube to discharge the gas is substantially independent of the gas pressure existing in the large space, so that in this proposed form of cartridge the previously mentioned problem of bulk and recoil need not be interrelated. However, the problems and disadvantages mentioned in sub-paragraphs (a), (b) and (c) above have to be overcome.
The present invention generally concerns a rechargeable cartridge which has some similarity with that disclosed in Swiss Pat. No. 16072 of 1898, in that the cartridge is generally of a kind (hereinafter referred to as "the said kind") comprising a casing having a hollow interior within which is provided an internal gas storage space, which space is disposed between a hollow discharge (front) end portion of the casing and a hollow base (rear) end portion of the casing; and further comprising actuating means actuable to cause gas to be discharged from the storage space into said hollow discharge end portion, said actuating means having a movable member, which extends longitudinally within said internal gas storage space to said discharge end portion, and having a base end part accessible for striking by a firing pin for actuation of the actuating means.
An object of the present invention is to enable all these disadvantages and problems to be overcome or reduced.